Lung transplantation is an established therapy for the treatment of end-stage lung diseases. Despite increasing experience, survival remains lower than for other solid organ transplants due to infection and rejection (both acute and chronic). Systemic cyclosporine based immunotherapy does not provide consistent control of rejection and is associated with serious adverse side effects. Our experiments on locally delivered cyclosporine, via aerosol, have proven its efficacy in preventing acute pulmonary rejection. The rationale is that the intra-graft milieu is of critical importance in the sensitization and maturation of immune responsive cells. We propose to better define the intra-graft milieu during early allograft rejection and to determine the mechanisms by which locally delivered immunosuppressive agents more effectively prevent the rejection process. The studies will focus on the differences between locally and systemically delivered CsA. We will serially measure the immunoregulatory cytokines IL-2, IL-4, IL-10 and IFNg to examine differences between local and systemic therapy in the generation of message (mRNA) for these cytokines. In parallel studies we will examine the effect of local versus systemic delivery of CsA on the generation and maturation of functional cytotoxic T cells using in vitro lymphocyte assays. Allo-immune responses in rejection and its component parts, host-versus-graft reaction and graft-versus-host response will be studied. Our working hypothesis is that both local and systemic CsA act through similar mechanisms but that local CsA interferes with cytokine production and T-cell maturation more efficiently by inhibiting the allo-immune response much earlier in rejection. We will compare these results with our historical studies on sponge matrix allografts. Delivery of CsA into the graft may also depress T-cell mediated host responses to infection and other white cell responses. We will examine how local delivery alters the immunocompetence of these defenses against infection by examining the clearance of bacteria inoculated into the graft. The important question is whether local delivery of CsA confers an increased risk for local (pneumonia) or systemic infection. These studies are of particular importance as we are about to initiate an IRB and FDA approved clinical trial of aerosol CsA in the treatment of patients with severe refractory pulmonary rejection.